P0315 P0xxx · Powertrain (P) Low severity
Crankshaft Position System Variation Not Learned
The ECU has lost its learned crankshaft position variation values, which it uses to detect misfire accurately. Common after an ECU replacement, a flywheel change or a software update.
Severity guidance: Low — usually no drivability impact, fix at the next service
Symptoms you will notice
- Misfire detection unreliable
- Possible no-start after a relearn
- No obvious drivability issue
Common causes
Ordered from most to least likely — start at the top.
- 1 ECU replaced or reflashed without a relearn
- 2 New or resurfaced flywheel / flexplate
- 3 Crankshaft reluctor damage
- 4 Weak battery interrupting the learn procedure
How to diagnose it
Cheapest and least invasive first — most of these codes are not a parts problem.
- ✓ Check whether the vehicle has recently had ECU or clutch work — that is the usual story.
- ✓ Run the manufacturer's crankshaft variation relearn procedure with a capable scan tool.
- ✓ Ensure battery voltage is stable above 12.4 V during the procedure.
- ✓ Inspect the reluctor wheel if the relearn will not complete.
Repair options
- Perform the CKP variation relearn
- Replace a damaged reluctor or flywheel
- Stabilise the charging system
P0315 — frequently asked questions
Can I clear the code and drive away? +
It will come back and misfire monitoring stays disabled. Do the relearn properly.
Does every car need this procedure? +
Most modern petrol engines do. Check the service manual for the specific decel-fuel-cutoff routine.
Confirm the diagnosis before you buy parts
Send us the code, freeze-frame data and the vehicle — our engineers will tell you what to test first.